[platform-ant-dev] External tool variable change

[Jared Burns <jared-eclipse@xxxxxxxxx>]

Currently, external tools defines variables in the plugin.xml on a 
per-attribute basis. There are variables for the location attribute, 
variables for the working directory attribute, and variables for the 
arguments attribute.

The current mechanism is heavy on duplication - each variable has to be fully 
redefined for each scope in which it's valid - and light on flexibility - why 
would we want to limit which variables our users have access to?

I'm proposing that we switch to a single extension point for the variables, 
thus reducing duplication and allowing users access to all variables in all 
fields. I've already talked about this with DarinS, so I'm going to get 
started on the conversion immediately.

If anyone can think of a reason that we'd want to keep the three separate 
extension points, please speak up.

Thanks,
- Jared